Role of Cancer Cell Phenotype on the Differential Intracellular Transport and Localization of Quantum Dots

A wide array of nanoparticles, based on inorganic materials, metals, polymers, and lipids, is being investigated as therapeutics and imaging agents in cancer disease. Cancer disease progression to the aggressive metastatic state is a result of the accumulation of various genetic changes which leads to phenotypic alterations. However, the role of the cancer cell phenotype on the uptake, sorting, and intracellular fate of delivered nanoparticles remains poorly understood. We report that phenotypic differences, which are a hallmark of the heterogeneous nature of epithelial tumors, can lead to dramatic differences in intracellular sorting, trafficking and localization of nanoparticles in cancer cells. Unconjugated anionic quantum dots demonstrated different intracellular profiles in three closely related human prostate cancer cells used in the current investigation: PC3, PC3-flu, and PC3-PSMA. Our results demonstrate that unconjugated anionic quantum dots are spontaneously taken up by these cancer cells which then sort and transport these to dramatically different fates. Serum proteins and conjugated molecules such as targeting antibodies or cell penetrating peptides are not necessary for the uptake and trafficking of nanoparticles in these cells. Following internalization from clathrin-coated pits, nanoparticles are trafficked in vesicles along microtubules to the sorting endosomal complex in these non-polarized cells. At this stage, nanoparticles are destined for different fates depending on the cellular phenotype. Quantum dots demonstrated punctated intracellular localization throughout the cytoplasm in PC3 cells indicating that they were trafficked along the lysozomal degradation pathway. However, in PC3-PSMA cells, the nanoparticles were sorted and transported along microtubules to a single juxtanuclear location (‘dot-of-dots’) to the perinuclear recycling compartment (PNRC) near the microtubule organizing center (MTOC), where they colocalized with transferrin and the Prostate-Specific Membrane Antigen (PSMA). To our knowledge this is the first demonstration of the localization of unconjugated nanoparticles at the MTOC. In addition, our results clearly indicate that nanoparticle sorting and transport is influenced by changes in cancer cell phenotype, and can have significant implications in the design and engineering of nanoscale drug delivery and imaging systems for advanced tumors.